It is common practice in incubators of reaction vessels containing sample and reagent, to process them by carrying them in two independently-driven, concentrically mounted rotors, using a transfer mechanism to move a vessel from one rotor to the other as needed, to complete the processing. Such devices are shown in, e.g., U.S. Pat. Nos. 4,699,766 and 5,244,633. In the former, the transfer occurs by an elevator that raises the vessel above the first rotor, moves it linearly to a position above the second rotor, and drops it into the second rotor. In the '633 patent, a push rod merely pushes the vessel across from one rotor to the other via slots located in the rotor for this purpose.
In either case, the transfer mechanism is quite elaborate. For example, the description in the '766 patent (column 4, lines 47-49) is of the use of an elevator that must grip the vessel, raise and move it linearly, lower it and then ungrip it (the details of which, however, are not shown). Such involved and complex mechanisms do not lend themselves either to a) inexpensive manufacture or b) reduced maintenance during operation.
Thus, there has been a need prior to this invention to provide a transfer mechanism between rotors of an incubator using, for example, an elevator that is simplified in construction, leading to reduced costs of manufacture and maintenance.